This invention lies in the area of ink jet apparatus and, more particularly, ink jet apparatus utilizing hot melt ink and having a normally vented reservoir.
The use of hot melt ink in ink jet systems, which ink is normally in a solid or frozen state but attains a liquid state of phase when its temperature is raised, has presented a number of advantages to ink jet apparatus. For a discussion of the characteristics of such ink and the uses thereof, reference is made to U.S. Pat. No. 4,390,369 and pending U.S. applications U.S. Ser. No. 610,627, filed May 16, 1984; Ser. No. 565,127, filed Dec. 23, 1983; and Ser. No. 644,452, filed Aug. 27, 1984, all assigned to the same assignee as this invention and incorporated herein by reference.
The use of hot melt ink creates special design needs for the reservoir system. It is necessary periodically to receive an ink pellet, melt it and drain the melted ink through a fill port into the reservoir. Also, it is necessary to have an air vent for normally venting the reservoir to atmospheric air. At the same time, any design must take into account the fact that the use of hot melt ink creates a special need for frequent repriming of the system. One of the characteristics of hot melt ink is that it degenerates faster the longer it is maintained in its liquid phase, with the result that it is advantageous to permit cooling and freezing of the ink when the apparatus is not in use. However, the hot melt ink contracts when it cools to a temperature below the melting point, which contraction of the ink results in depriming of the system. Thus, such hot melt ink apparatus has an increased need for an efficient repriming system.
The fact that the hot melt ink must be vented to atmosphere creates a safety problem. The ink is maintained at about 200.degree. F., and an operator who carries or lifts the appartatus before the ink has cooled runs a danger of spilling that hot ink. Thus, some means of automatically preventing spillage is required.
The above noted characteristics of hot melt ink systems lead to the design requirement of a two way valve, which valve acts as both as an air vent and as a fill port in its normally opened position, and which can be operated to a closed position when priming of the reservoir is undertaken. At the same time, there is a need, not previously met, for means to automatically close the valve, or port, under any circumstance where the reservoir is tilted to a degree where there is a likelihood of spillage of ink due to the tilting. A tilt valve has been utilized in the area of storage batteries, but such valve provides only an air vent and does not comprise a fill port.